Energy-curable news ink containing soy oil

ABSTRACT

An energy curable ink composition comprising an acrylate-functional derivative of soybean oil and one or more further acrylate-functional materials is suitable for printing on a cold-set lithographic press and is cured by exposure to an actinic radiation source located on the press.

FIELD OF THE INVENTION

The invention relates to energy-curing ink compositions and methods.

BACKGROUND OF THE INVENTION

Newspapers are predominantly printed lithographically with cold-set inksthat set by penetration into the absorbent paper stock. Printer whoprint daily newspapers may devote considerable press time to it, butthose printer who print newspapers for smaller towns and cities thatpublish only weekly or bi-weekly may find considerable downtime. Thepresses represent a costly investment, and it is desirable to haveenough jobs to fill available time. Consequently, printers may seekother jobs such as insert material, covers, and color advertisements.Many of these print jobs, however, require heatset equipment to print oncoated stock for printed materials with better gloss or better printdefinition. The cold-set process is capable of printing only on uncoated(thus absorbent) stock.

Modifying the press to print heatset inks would require significantadditional equipment to be added, particularly ovens and solvent reclaimor incineration equipment. This would add a lot of expense and require alot of additional space. Further, the heatset inks would need to becompatible with the rollers and blankets of the press, which are rubbermaterials.

SUMMARY OF THE INVENTION

The present invention provides an energy curable ink compositionincluding an acrylate-functional derivative of soybean oil and one ormore further acrylate-functional materials. In various embodiments, thecomposition has a soy content of at least about 7% by weight of soy. Theink compositions may be cured by electron beam radiation or, ifphotoinitiators are further included in the inks, by ultraviolet (UV)radiation the ink of the invention uses a naturally occurring material,soybean oil from a sustainable source. The ink provides improvedcharacteristics, particularly excellent color strength mileage,ink/water balance, and smoothness.

The invention also provides a method of printing with a lithographicprinting press, wherein a cold-set ink is printed on an absorbentsubstrate and, subsequently, an energy curable ink composition includingan acrylate-functional derivative of soybean oil and one or moreacrylate-functional oligomers is printed onto a nonabsorbent orsemi-absorbent substrate and then cured with actinic radiation. Theactinic radiation may be electron beam radiation or, if a photoinitiatoris included in the energy curable ink composition, ultravioletradiation. In various embodiments, the oligomers may be selected frompolyester acrylates, polyurethane acrylates, epoxy acrylates, andcombinations of these.

The invention also provides a newspaper cold-set lithographic pressequipped with a source of actinic radiation, particularly an electronbeam radiation source or an ultraviolet light radiation source. Thepress is suitable for printing an energy curable ink compositionincluding an acrylate-functional derivative of soybean oil and one ormore acrylate-functional oligomers

“A” and “an” as used herein indicate “at least one” of the item ispresent; a plurality of such items may be present, when possible.“About” when applied to values indicates that the calculation or themeasurement allows some slight imprecision in the value (with someapproach to exactness in the value; approximately or reasonably close tothe value; nearly). If, for some reason, the imprecision provided by“about” is not otherwise understood in the art with this ordinarymeaning, then “about” as used herein indicates a possible variation ofup to 5% in the value.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

The energy curable ink composition includes an acrylate-functionalderivative of soybean oil (“soy acrylate”) and one or more furtheracrylate-functional materials. In various embodiments, the inkcomposition includes preferably at least about 7% by weight of the soyacrylate, more preferably at least about 8% by weight of the soyacrylate, and still more preferably at least about 9% by weight of thesoy acrylate. The ink composition includes preferably up to about 12% byweight of the soy acrylate, more preferably up to about 10% by weight ofthe soy acrylate.

An acrylate-functional derivative of soybean oil may be prepared byvarious means by adducting soybean oil components with functionalityreactive with acrylic acid or a functional derivative of acrylic acid.In a preferred embodiment, epoxidized soybean oil is reacted withacrylic acid to provide the beta-hydroxy acrylate ester, known asepoxidized soybean oil acrylate. Epoxidized soybean oil and its acrylateare both commercially available. Preparation of acrylated fatty oilssuch as soybean oil is described in Hodakowski et al., U.S. Pat. No.4,119,640, which is incorporated herein by reference. Other methods ofsynthesizing acrylate-functional soybean oil derivatives, such as betransesterification with acrylic acid or by reaction of epoxidizedsoybean oil with t-butylaminoethyl acrylate, are also feasible.

In addition to the soy acrylate, the energy-curable lithographic inks ofthe invention also include one or more other acrylate-functionalmaterials, which may be acrylate monomers and/or oligomers. Preferably,the inks include at least one or more acrylate oligomer. The acrylatemonomers and oligomers should be selected and apportioned to provide asuitable viscosity for lithographic printing. In general, acrylatematerials are preferred over methacrylate or vinyl materials because theacrylate materials have faster cure rates, although the compositions mayinclude methacrylate- and/or vinyl-functional monomers as well.

The monomer or monomers in the ink composition may be monoethylenicallyfunctional or polyethylenically functional, and preferably difunctional,trifunctional, and/or tetrafunctional monomers are included. Suitableexamples of acrylate monomers include, without limitation,neopentylglycol diacrylate, pentaerythritol tetracrylate,trimethylolpropane triacrylate, hexanediol diacrylate, isobomylacrylate, bisphenol A epoxy diacrylate, triethyleneglycol diacrylate,ethoxylated bisphenol-A diacrylate, tripropyleneglycol diacrylate,ethoxylated hexanediol diacrylate, propoxylated glyceryl triacrylate,and so on. These may be used in any combination.

Suitable examples of acrylate oligomers include, without limitation,polyester acrylates, polyether acrylates, epoxy acrylates, and urethaneacrylates. Such oligomers are well-known and described in detail in manyreferences. Many are commercially available. In general,acrylate-functional oligomers may be formed by preparing an compound oroligomeric material having one or more functional groups reactive withan acrylate monomer, such as with acrylic acid. Acrylate oligomerstypically have a number average molecular weight of from 500 to 5000.

Polyester acrylates may be prepared, for example, by synthesis of apolyester oligomer using acrylic acid and/or hydroxyalkyl esters ofacrylic acid as reactant. Preferably, however, polyester acrylates areprepared by acrylating hydroxyl-functional polyesters. Unreacted acrylicacid may be removed from the product by washing, distilling, or,preferably, by reacting with an equivalent amount of a monoepoxide ordiepoxide compound using appropriate catalysts, such astriphenylphosphine, for example.

Polyether acrylates may be prepared by esterifying hydroxyl-functionalpolyethers with acrylic acid. Hydroxy-functional polyethers may beprepared by reacting dihydric and/or higher polyhydric alcohols withdesired amounts of ethylene oxide and/or propylene oxide in accordancewith well-known methods. It is also possible to use polymerizationproducts of tetrahydrofuran or butylene oxide.

Epoxy acrylates may be prepared by subjecting acrylic acid to additionreaction with epoxy resins, for example, with epoxy resins based onbisphenol A.

Polyurethane acrylates may be obtained by reacting a diisocyanate orpolyisocyanate with one or more chain extenders from the group of diols,polyols, diamines, polyamines (which would provide urea groups), and/oralkanolamines, and then reacting some or all of the remaining freeisocyanate groups with at least one hydroxyalkyl acrylate or aminoalkylacrylate. Another possibility is to prepare the polyurethane acrylatesby first reacting some of the isocyanate groups of a diisocyanate orpolyisocyanate with at least one hydroxyalkyl acrylate and then to reactthe remaining isocyanate groups with a chain extender.

The ink may contain further ethylenically unsaturated reactants, such asmethacrylate monomers and oligomers and vinyl monomers and oligomers. Ifincluded, these further materials are generally used in small amountsdue their lower reactivity.

The ink will contain one or more pigments to provide a desired color.Suitable pigments include, without limitation, inorganic pigments suchas carbon black, titanium dioxide, black iron oxide, and so on; andorganic pigments such as azo pigments such as lithol reds (e.g., calciumlithol red, barium lithol red), rubine reds, and naphthol reds, oranges,and browns; monoarylide and diarylide pigments such as diarylide yellow,phthalocyanine blue and green pigments, azomethine pigments, methinepigments, anthraquinone pigments, perinone pigments, perylene pigments,diketopyrrolopyrrole pigments, thioindigo pigments, iminoisoindolinepigments, iminoisoindolinone pigments, quinacridone pigments such asquinacridone reds and violets, flavanthrone pigments, indanthronepigments, anthrapyrimidine pigments, carbazole pigments such ascarbazole violet, benzimidazolone yellows, tolyl orange, naphtholorange, and quinophthalone pigments and so on. The pigments may be usedsingly or in any combination.

The ink may contain any desired additives known in the art. Illustrativeexamples of other additives include, without limitation, surfactants,wetting agents, waxes, emulsifying agents and dispersing agents,antioxidants, flow agents and other rheology modifiers, gloss enhancers,and anti-settling agents. When included, additives are typicallyincluded in amounts of at least about 0.001% of the ink composition, andmay be included in amount of about 7% by weight or more of the inkcomposition.

The applied ink is cured with actinic radiation. If photoinitiators arefurther included in the inks, the inks may be cured by ultraviolet (UV)radiation. Various UV light sources, including iron oxide or gallium orvaladium doped mercury lamps and xenon chloride lamps, are available.Electron beam sources are also preferred.

Examples of suitable photoinitiators include, without limitation,benzophenone, benzophenone derivatives, acetophenone, acetophenonederivatives, for example 1-hydroxy-cyclohexyl-phenyl ketone,1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one or2-hydroxy-2-methyl-1-phenyl-propanone, dialkoxyacetophenones,.alpha.-hydroxy- or .alpha.-amino-acetophenones, for example(4-morpholino-benzoyl)-1-benzyl-1-di-methylamino-propane or(4-methylthiobenzoyl)-1-methyl-1-morpholino-ethane,4-aroyl-1,3-dioxolanes, benzoin alkyl ethers and benzil ketals, forexample 2,2-dimethoxy-1,2-diphenylethan-1-one, monoacylphosphine oxides,for example 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide,bisacylphosphine oxides, for examplebis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide,bis(2,4,6-trimethylbenzoyl)-(2-methylprop-1-yl)-phosphine oxide,bis(2,4,6-trimethylbenzoyl)phenyl-phosphine oxide and trisacylphosphineoxides. In certain cases it may be advantageous to use mixtures of twoor more photoinitiators, for example mixtures ofbis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide orbis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide with1-hydroxy-cyclohexyl-phenyl ketone orhydroxy-2-methyl-1-phenyl-propanone or2-methoxy-1-phenyl-ethane-1,2dione, and thioxanphones. Thephotoinitiator or photoinitiators may be included in amounts of fromabout 4 percent to about 20 percent by weight, preferably from about 5percent to about 10 percent by weight in the ink.

When the energy curable inks are cured by ultraviolet radiation, it ispossible to shorten the curing time by adding a photosensitizer, such asbenzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropylether, benzil (dibenzoyl), diphenyl disulfide, tetrame-thylthiuram-monosulfide, diacetyl, azobisisobutyronitrile,2-methyl-anthraquinone, 2-ethyl-anthraquinone or2-tertbutyl-anthraquinone, along with the photoinitiator orphotoinitiators. A photosensitizer may be included preferably at most 5%by weight based on the weight of the composition.

The inks of the invention are lithographically printed onto a substrate,preferably using a cold-set lithographic press augmented with an actinicradiation source for curing the inks. Suitable substrates include, forexamples, coated and uncoated papers. Thus, the press may be used toprint a cold-set print job, such as printing a newspaper with news ink,and then be used to print a coated stock using the energy-curable,soy-containing ink of the invention. The actinic radiation source(s) forcuring the ink is a fairly inexpensive, compact addition to the press.In various preferred embodiments, at least one UV lamp is installed in aposition to cure the energy-curable ink after it is printed on thesubstrate. Preferably, at least one actinic radiation source (preferablya UV lamp) is installed on each side of the web.

The invention is illustrated by the following examples. The examples aremerely illustrative and do not in any way limit the scope of theinvention as described and claimed. All parts are parts by weight unlessotherwise noted. Example.

An energy-curable ink is prepared by combining 7 parts by weight of aphotoinitiator, 25 parts by weight of a combination of isobomyl acrylateand trimethylolpropane triacrylate, 25 parts by weight of a polyesteracrylate, 15 parts by weight of a bisphenol A-type epoxy acrylate, 8parts by weight of the acrylate ester of epoxidized soybean oil, 18parts by weight carbon black, 5 parts by weight of a urethane acrylate,and 5 parts by weight of a combination of UV ink additives.

A cold-set lithographic press equipped with an ultraviolet radiationlamp is used to print a newspaper run. After the printing is completed,the news ink in the ink fountain is replaced by the energy-curable ink.An insert is then printed on coated paper with the energy-curable ink.The printed ink is cured with ultraviolet radiation from the lamp.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. An energy curable ink composition comprising an acrylate-functionalderivative of soybean oil and one or more further acrylate-functionalmaterials, wherein the ink composition is suitable for printing on acold-set lithographic press.
 2. An energy curable ink compositionaccording to claim 1, further comprising a photoinitiator.
 3. An energycurable ink composition according to claim 1, wherein theacrylate-functional derivative of soybean oil comprises epoxidizedsoybean oil acrylate.
 4. An energy curable ink composition according toclaim 1, comprising at least about 7% by weight of theacrylate-functional derivative of soybean oil.
 5. An energy curable inkcomposition according to claim 1, comprising up to about 12% by weightof the acrylate-functional derivative of soybean oil.
 6. An energycurable ink composition according to claim 1, comprising an acrylateoligomer selected from the group consisting of polyester acrylates,polyether acrylates, epoxy acrylates, urethane acrylates, andcombinations thereof.
 7. A method of printing with a newspaper cold-setlithographic press, comprising steps of: printing a newspaper withcold-set news ink; printing an energy curable ink composition comprisingan acrylate-functional derivative of soybean oil and one or more furtheracrylate-functional materials, curing the printed ink with actinicradiation from a source located on the press.
 8. A method according toclaim 7, wherein the source comprises an ultraviolet radiation lamp. 9.A method according to claim 7, wherein the ink comprises epoxidizedsoybean oil acrylate.
 10. A method according to claim 7, wherein the inkcomprises at least about 7% by weight of epoxidized soybean oilacrylate.
 11. A newspaper cold-set lithographic press comprising asource of actinic radiation.
 12. A press according to claim 11,comprising at least one ultraviolet radiation lamp located on each sideof a web.